Problem: Simplify the following expression: $n = \dfrac{-9q}{4} - \dfrac{9q}{4}$
Since the expressions have the same denominator we simply combine the numerators: $n = \dfrac{-9q - (9q)}{4}$ Combine like terms: $n = \dfrac{-18q}{4}$ Simplify by dividing numerator and denominator by 2: $n = \dfrac{-9q}{2}$